Formation of Alkynylgermyl-Substituted Germylenes via a Catenation of Ge Atoms.

Reactions of amidinate-stabilized germylene chlorides R1Ge(:)Cl (R1 = PhC(NtBu)2) and R2Ge(:)Cl (R2 = PhC(NCy)2, Cy = cyclohexanyl) with trimethylsilylethynyl lithium salt (LLi, L = -C≡CTMS) afforded alkynylgermyl-substituted germylenes R1(:)Ge-GeL3 (1) and [R2GeL2]2Ge(:) (2), respectively. Both of them may undergo the formation of Ge-Ge single bonds with a concomitant 1,2-shift of ethynyl groups. DFT calculations determined the reaction pathways where two possible intermediates (:)GeL2 and RGe(:)L (R = R1, R2) are proposed, which were consistent with the trapping reactions of (:)GeL2 toward IAr-(:)GeL2 (3, IAr = :C{N(Ar)CH}2, Ar = 2,6-iPr2C6H3). The reaction of 1 with N3TMS gave a new aminogermylene R1(:)Ge-N(TMS)-GeL3 (4), indicating a reactive Ge-Ge bond.